Fix 532, 533, 641 (#642)

boa/src/exec/mod.rs

@@ -148,6 +148,10 @@ impl Interpreter {
         let new_func = Object::function(func, function_prototype);
 
         let val = Value::from(new_func);
+
+        // Set constructor field to the newly created Value (function object)
+        proto.set_field("constructor", val.clone());
+
         val.set_field(PROTOTYPE, proto);
         val.set_field("length", Value::from(params_len));
 

boa/src/exec/tests.rs

@@ -766,8 +766,11 @@ mod in_operator {
             var bar = new Foo();
         "#;
         forward(&mut engine, scenario);
-        let a = forward_val(&mut engine, "bar").unwrap();
-        assert!(a.as_object().unwrap().prototype().is_object());
+        let bar_val = forward_val(&mut engine, "bar").unwrap();
+        let bar_obj = bar_val.as_object().unwrap();
+        let foo_val = forward_val(&mut engine, "Foo").unwrap();
+        let foo_obj = foo_val.as_object().unwrap();
+        assert!(bar_obj.prototype().strict_equals(&foo_obj.get_field("prototype").unwrap()));
     }
 }